A2B5 lineages of human astrocytic tumors and their recurrence

Astrocytomas are very common intracranial glial cell neoplasms with an inherent tendency to progress. However, the heterogeneity of the morphological features and clinical behavior of the tumors makes accurate prognosis based on the histopathological grading system very difficult. Studies demonstrated that astrocytes have two distinctive cell lineages, and tumors arisen from these two astrocytic lineages have been speculated to have different biological and clinical manifestations. The present study aimed to delineate these two astrocytic lineages in human astrocytomas by using different immunohistochemical markers and to correlate the cell lineages of the tumors with their recurrence. Three markers were used, namely the A2B5 antigen, which is present in type 2 astrocytes but absent in type 1 astrocytes, glial fibrillary acidic protein (GFAP), a marker for astrocytes, and galactocerebroside (GC), a marker for oligodendrocytes. It was found that astrocytomas sharing the A2B5+ lineage (A2B5 positive and GFAP positive) have a significantly higher recurrence rate than the tumors of the A2B5− lineage (A2B5 negative and GFAP positive). Immunohistochemical staining and PCR-single-stranded conformational polymorphism analysis showed that p53 overexpression and p53 mutations were closely associated with the recurrent astrocytomas, and p53 abnormalities were more frequently detected in astrocytomas of the A2B5+ lineage. Quantification of proliferation by counting argyrophil nucleolar organizer regions (AgNORs) indicated a higher AgNOR count in the A2B5+ lineage than the A2B5− lineage. Our findings thus suggest that astrocytomas share similar antigenicity with astrocytes, and that the A2B5+ lineage exhibited a higher recurrence rate than the A2B5− lineage. The higher recurrence rate of the A2B5+ tumors may be in part related to the higher frequency of p53 abnormalities found in the tumors and the higher proliferative activity as reflected by the higher AgNOR count of the tumors.